Portion of a sole bottom surface



FIG. 1 is a bottom plan view of a portion of a sole bottom surface showing my new design;

FIG. 2 is a profile view of the portion of a sole bottom surface taken along line 2--2 of FIG. 1; and,

FIG. 3 is a profile view of the portion of a sole bottom surface taken long line 3--3 of FIG. 1.

The broken line showing of a sole periphery and the cross-hatching in FIGS. 2 and 3 is for illustrative purposes and forms no part of the claimed design. 

The ornamental design for a portion of a sole bottom surface, as shown and described. 